Resistance of several Indonesian cereal grain cultivars to the maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae)

The maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), is a primary pest and internal feeder of cereal grains, responsible for substantial economic losses worldwide, including in Indonesia. This study assessed the host preference and biological performance of the maize weevil on several Indonesian cereal grains, including milled rice (IR64), unhulled rice (Mekongga), maize seed (Jakarin), and sorghum seed (Soper 7). In a free-choice preference test, sorghum seed was the most preferred host for adult weevils to feed on and lay eggs, followed by milled rice, maize seed, and unhulled rice. The susceptibility index from the antibiosis test indicated that unhulled rice and maize seed were resistant, whereas milled rice and sorghum seed were classified as susceptible. The preadult period (38.11-43.43 days) and median development period (30.13-41.63 days) of S. zeamais were positively correlated with tannin, phenolic, and carbohydrate contents in the grains. Conversely, the preadult period, median development period, and F1 progeny were negatively correlated with grain hardness and lipid content, while grain moisture content showed a negative correlation with the preadult period and median development period. Additionally, the seed coat on unhulled rice appeared to act as a barrier that inhibited feeding and oviposition by S. zeamais. Therefore, the host preference and biology of S. zeamais were associated with the physicochemical properties of the evaluated cereal grains. Consequently, evaluating the susceptibility of cereal grains to S. zeamais is fundamental for developing effective integrated pest management strategies to mitigate the economic impact of this pest.